Grafting of ethylenically unsaturated monomers onto polymers

ABSTRACT

The present invention relates to a process for the preparation of grafted polymers wherein in a first step A) a stable nitroxyl radical is grafted onto a polymer, which step comprises heating a polymer and a stable nitroxyl radical (NO.); and in a second step B) the grafted polymer of step A) is heated in the presence of an ethylenically unsaturated monomer or oligomer to a temperature at which cleavage of the nitroxyl-polymer bond occurs and polymerization of the ethylenically unsaturated monomer or oligomer is initiated at the polymer radical; maintaining said temperature for further polymerization and afterwards cooling down the mixture to a temperature below 60° C. Further subjects are grafted polymers prepared by said process, the use of the polymeric radical initiator and the use of NO radicals for grafting polymers.

The present invention relates to a process for the preparation of grafted polymers wherein in a first step A) a stable nitroxyl radical is grafted onto a polymer, which step comprises heating a polymer and a compound containing a stable NO. radical to above the melting point of the polymer, mixing and reacting the components at said temperature; and in a second step B) the grafted polymer of step A) is heated in the presence of an ethylenically unsaturated monomer or oligomer to a temperature at which cleavage of the nitroxyl-polymer bond occurs. Further subjects of the present invention are grafted polymers prepared by said process, the use of the polymeric radical initiator and the use of a stable NO radical for grafting polymers.

Increasing activities have been directed towards chemical modifications of existing polymers in order to obtain functional and/or engineered new material. Chemical modifications of existing polymers are important for at least two reasons: 1. They can be an inexpensive and rapid way of obtaining new polymers without having to search for new monomers; 2. they may be the only way to synthesize polymers with the intended new characteristics.

An important chemical modification is the free radical grafting of reactive monomers, which involves reaction of a polymer with a vinyl-group containing monomer or mixture of monomers capable of forming grafts onto the polymer backbone. If the grafts are long, the modified polymer becomes a true graft copolymer, of which the properties will be very different from those of the original polymer substrate. When the grafts are short with less than, for example five moieties, most of the physical and or mechanical properties of the modified polymer substrate will be retained. The properties are furthermore influenced by the structure of the grafted monomer. For example grafting of a polar monomer onto a non polar polymer such as polyethylene, results in decisively modified properties such as adhesion to other substrates, compatibility with polar surfaces, even at short chain lengths.

The advantages of free radical-grafting are further gained with the use of batch mixers or screw extruders as chemical reactors, which allow the free radical-grafting reaction to occur without solvents. This is for example described by G. H. Hu et al., in “Reactive Modifiers for Polymers”, first edition, Blackie Academic & Professional an Imprint of Chapman & Hall, London 1997, chapter 1, pages 1-97.

These free radical-grafting reactions are usually performed in the presence of a free radical source such as a peroxide and a reactive monomer, such as for example acrylic acid. However the use of free radical sources such as peroxides may cause undesired properties and lead to problems during processing (gel formation, crosslinking, molecular weight reduction) or during use. Typically the long term stability is reduced and/or the polymer cannot anymore be used in outdoor applications or in applications at elevated temperatures.

EP-A-621 878 discloses a free radical polymerization process which controls the growth of polymer chains to produce short chain or oligomeric homopolymers and copolymers, including block and graft copolymers. The process employs a stable free radical as for example of formula (in part) R′R″N—O. and a free radical initiator.

Surprisingly it has now been found that with such R′R″N—O. compounds it is possible to produce a polymeric radical initiator by grafting the group R′R″N—O to the polymer and to use this macroinitiator for further grafting reactions of olefinically unsaturated monomers.

The polymerization processes and resin products of the present invention are useful in many applications, including a variety of specialty applications, such as for the preparation of grafted block copolymers which are useful as compatibilizing agents for polymer blends, adhesion promoters or dispersing agents for coating systems.

One subject of the present invention is a process for the preparation of a grafted polymer wherein in a first step

A) a stable nitroxyl radical is grafted onto a polymer, which step comprises heating a polymer and a stable nitroxyl radical (NO.); and in a second step

B) the grafted polymer of step A) is heated in the presence of an ethylenically unsaturated monomer or oligomer to a temperature at which cleavage of the nitroxyl-polymer bond occurs and polymerization of the ethylenically unsaturated monomer or oligomer is initiated at the polymer radical; maintaining said temperature for further polymerization and afterwards cooling down the mixture to a temperature below 60° C.

The reaction mixture after step A) may also be cooled down to a temperature below 60° C. before further reaction of step B) is performed.

Optionally a free radical source is additionally present.

Preferably the free radical source is a bis-azo compound, a peroxide or a hydroperoxide.

Specific preferred radical sources are 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-methyl-butyronitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1′-azobis(1-cyclohexanecarbonitrile), 2,2′-azobis(isobutyramide)dehydrate, 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile, dimethyl-2,2′-azobisisobutyrate, 2-(carbamoylazo)isobutyronitrile, 2,2′-azobis(2,4,4-trimethylpentane), 2,2′-azobis(2-methylpropane), 2,2′-azobis(N,N′-dimethyleneisobutyramidine), free base or hydrochloride, 2,2′-azobis(2-amidinopropane), free base or hydrochloride, 2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide} or 2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide; acetyl cyclohexane sulphonyl peroxide, diisopropyl peroxy dicarbonate, t-amyl perneodecanoate, t-butyl perneodecanoate, t-butyl perpivalate, t-amylperpivalate, bis(2,4-dichlorobenzoyl)peroxide, diisononanoyl peroxide, didecanoyl peroxide, dioctanoyl peroxide, dilauroyl peroxide, bis(2-methylbenzoyl)peroxide, disuccinic acid peroxide, diacetyl peroxide, dibenzoyl peroxide, t-butyl per 2-ethylhexanoate, bis-(4-chlorobenzoyl)-peroxide, t-butyl perisobutyrate, t-butyl permaleinate, 1,1-bis(t-butylperoxy)3,5,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, t-butyl peroxy isopropyl carbonate, t-butyl perisononaoate, 2,5-dimethylhexane 2,5-dibenzoate, t-butyl peracetate, t-amyl perbenzoate, t-butyl perbenzoate, 2,2-bis(t-butylperoxy)butane, 2,2 bis(t-butylperoxy)propane, dicumyl peroxide, 2,5-dimethylhexane-2,5-di-t-butylperoxide, 3-t-butylperoxy 3-phenyiphthalide, di-t-amyl peroxide, α,α′-bis(t-butylperoxy isopropyl)benzene, 3,5-bis(t-butylperoxy)3,5-dimethyl 1,2-dioxolane, di-t-butyl peroxide, 2,5-dimethylhexane-2,5-di-t-butylperoxide, 3,3,6,6,9,9-hexamethyl 1,2,4,5-tetraoxa cyclononane, p-menthane hydroperoxide, pinane hydroperoxide, diisopropylbenzene mono-α-hydroperoxide, cumene hydroperoxide or t-butyl hydroperoxide.

Peroxides are most preferred.

Examples of suitable polymers are mentioned below.

1. Polymers of monoolefins and diolefins, for example polypropylene, polyisobutylene, polybut-1-ene, poly-4-methylpent-1-ene, polyisoprene or polybutadiene, as well as polymers of cycloolefins, for instance of cyclopentene or norbornene, polyethylene (which optionally can be crosslinked), for example high density polyethylene (HDPE), high density and high molecular weight polyethylene (HDPE-HMW), high density and ultrahigh molecular weight polyethylene (HDPE-UHMW), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), (VLDPE) and (ULDPE).

Polyolefins, i.e. the polymers of monoolefins exemplified in the preceding paragraph, preferably polyethylene and polypropylene, can be prepared by different, and especially by the following, methods:

a) radical polymerisation (normally under high pressure and at elevated temperature).

b) catalytic polymerisation using a catalyst that normally contains one or more than one metal of groups IVb, Vb, VIb or VII of the Periodic Table. These metals usually have one or more than one ligand, typically oxides, halides, alcoholates, esters, ethers, amines, alkyls, alkenyls and/or aryls that may be either p- or s-coordinated. These metal complexes may be in the free form or fixed on substrates, typically on activated magnesium chloride, titanium(lll) chloride, alumina or silicon oxide. These catalysts may be soluble or insoluble in the polymerisation medium. The catalysts can be used by themselves in the polymerisation or further activators may be used, typically metal alkyls, metal hydrides, metal alkyl halides, metal alkyl oxides or metal alkyloxanes, said metals being elements of groups Ia, IIa and/or IIIa of the Periodic Table. The activators may be modified conveniently with further ester, ether, amine or silyl ether groups. These catalyst systems are usually termed Phillips, Standard Oil Indiana, Ziegler (-Natta), TNZ (DuPont), metallocene or single site catalysts (SSC).

2. Mixtures of the polymers mentioned under 1), for example mixtures of polypropylene with polyisobutylene, polypropylene with polyethylene (for example PP/HDPE, PP/LDPE) and mixtures of different types of polyethylene (for example LDPE/HDPE).

3. Copolymers of monoolefins and diolefins with each other or with other vinyl monomers, for example ethylene/propylene copolymers, linear low density polyethylene (LLDPE) and mixtures thereof with low density polyethylene (LDPE), propylene/but-1-ene copolymers, propylene/isobutylene copolymers, ethylene/but-1-ene copolymers, ethylene/hexene copolymers, ethylene/methylpentene copolymers, ethylene/heptene copolymers, ethylene/octene copolymers, propylene/butadiene copolymers, isobutylene/isoprene copolymers, ethylene/alkyl acrylate copolymers, ethylene/alkyl methacrylate copolymers, ethylene/vinyl acetate copolymers and their copolymers with carbon monoxide or ethylene/acrylic acid copolymers and their salts (ionomers) as well as terpolymers of ethylene with propylene and a diene such as hexadiene, dicyclopentadiene or ethylidene-norbornene; and mixtures of such copolymers with one another and with polymers mentioned in 1) above, for example polypropylene/ethylene-propylene copolymers, LDPE/ethylene-vinyl acetate copolymers (EVA), LDPE/ethylene-acrylic acid copolymers (EAA), LLDPE/EVA, LLDPE/EAA and alternating or random polyalkylene/carbon monoxide copolymers and mixtures thereof with other polymers, for example polyamides.

4. Hydrocarbon resins (for example C₅-C₉) including hydrogenated modifications thereof (e.g. tackifiers) and mixtures of polyalkylenes and starch.

5. Polystyrene, poly(p-methylstyrene), poly(a-methylstyrene).

6. Copolymers of styrene or a-methylstyrene with dienes or acrylic derivatives, for example styrene/butadiene, styrene/acrylonitrile, styrene/alkyl methacrylate, styrene/butadiene/alkyl acrylate, styrene/butadiene/alkyl methacrylate, styrene/maleic anhydride, styrene/acrylonitrile/methyl acrylate; mixtures of high impact strength of styrene copolymers and another polymer, for example a polyacrylate, a diene polymer or an ethylene/propylene/diene terpolymer; and block copolymers of styrene such as styrene/butadiene/styrene, styrene/isoprene/styrene, styrene/ethylene/butylene/styrene or styrene/ethylene/propylene/styrene.

7. Graft copolymers of styrene or a-methylstyrene, for example styrene on polybutadiene, styrene on polybutadiene-styrene or polybutadiene-acrylonitrile copolymers; styrene and acrylonitrile (or methacrylonitrile) on polybutadiene; styrene, acrylonitrile and methyl methacrylate on polybutadiene; styrene and maleic anhydride on polybutadiene; styrene, acrylonitrile and maleic anhydride or maleimide on polybutadiene; styrene and maleimide on polybutadiene; styrene and alkyl acrylates or methacrylates on polybutadiene; styrene and acrylonitrile on ethylene/propylene/diene terpolymers; styrene and acrylonitrile on polyalkyl acrylates or polyalkyl methacrylates, styrene and acrylonitrile on acrylate/butadiene copolymers, as well as mixtures thereof with the copolymers listed under 6), for example the copolymer mixtures known as ABS, MBS, ASA or AES polymers.

8. Halogen-containing polymers such as polychloroprene, chlorinated rubbers, chlorinated and brominated copolymer of isobutylene-isoprene (halobutyl rubber), chlorinated or sulfo-chlorinated polyethylene, copolymers of ethylene and chlorinated ethylene, epichlorohydrin homo- and copolymers, especially polymers of halogen-containing vinyl compounds, for example polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, as well as copolymers thereof such as vinyl chloride/vinylidene chloride, vinyl chloride/vinyl acetate or vinylidene chloride/vinyl acetate copolymers.

9. Polymers derived from α,β-unsaturated acids and derivatives thereof such as polyacrylates and polymethacrylates; polymethyl methacrylates, polyacrylamides and polyacrylonitriles, impact-modified with butyl acrylate.

10. Copolymers of the monomers mentioned under 9) with each other or with other unsaturated monomers, for example acrylonitrile/butadiene copolymers, acrylonitrile/alkyl acrylate copolymers, acrylonitrile/alkoxyalkyl acrylate or acrylonitrile/vinyl halide copolymers or acrylonitrile/ alkyl methacrylate/butadiene terpolymers.

11. Polymers derived from unsaturated alcohols and amines or the acyl derivatives or acetals thereof, for example polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, polyvinyl benzoate, polyvinyl maleate, polyvinyl butyral, polyallyl phthalate or polyallyl melamine; as well as their copolymers with olefins mentioned in 1) above.

12. Homopolymers and copolymers of cyclic ethers such as polyalkylene glycols, polyethylene oxide, polypropylene oxide or copolymers thereof with bisglycidyl ethers.

13. Polyacetals such as polyoxymethylene and those polyoxymethylenes which contain ethylene oxide as a comonomer; polyacetals modified with polyurethanes, acrylates or MBS.

14. Polyphenylene oxides and sulfides, and mixtures of polyphenylene oxides with styrene polymers or polyamides.

15. Polyurethanes derived from hydroxyl-terminated polyethers, polyesters or polybutadienes on the one hand and aliphatic or aromatic polyisocyanates on the other, as well as precursors thereof.

16. Polyamides and copolyamides derived from diamines and dicarboxylic acids and/or from aminocarboxylic acids or the corresponding lactams, for example polyamide 4, polyamide 6, polyamide 6/6, 6/10, 6/9, 6/12, 4/6, 12/12, polyamide 11, polyamide 12, aromatic polyamides starting from m-xylene diamine and adipic acid; polyamides prepared from hexamethylenediamine and isophthalic or/and terephthalic acid and with or without an elastomer as modifier, for example poly-2,4,4,-trimethylhexamethylene terephthalamide or poly-m-phenylene isophthalamide; and also block copolymers of the aforementioned polyamides with polyolefins, olefin copolymers, ionomers or chemically bonded or grafted elastomers; or with polyethers, e.g. with polyethylene glycol, polypropylene glycol or polytetramethylene glycol; as well as polyamides or copolyamides modified with EPDM or ABS; and polyamides condensed during processing (RIM polyamide systems).

17. Polyureas, polyimides, polyamide-imides, polyetherimids, polyesterimids, polyhydantoins and polybenzimidazoles.

18. Polyesters derived from dicarboxylic acids and diols and/or from hydroxycarboxylic acids or the corresponding lactones, for example polyethylene terephthalate, polybutylene terephthalate, poly-1,4-dimethylolcyclohexane terephthalate and polyhydroxybenzoates, as well as block copolyether esters derived from hydroxyl-terminated polyethers; and also polyesters modified with polycarbonates or MBS.

19. Polycarbonates and polyester carbonates.

20. Polysulfones, polyether sulfones and polyether ketones.

21. Blends of the aforementioned polymers (polyblends), for example PP/EPDM, Poly-amide/EPDM or ABS, PVC/EVA, PVC/ABS, PVC/MBS, PC/ABS, PBTP/ABS, PC/ASA, PC/PBT, PVC/CPE, PVC/acrylates, POM/PUR, PC/PUR, POM/acrylate, POM/MBS, PPO/HIPS, PPO/PA 6.6 and copolymers, PA/HDPE, PA/PP, PA/PPO, PBT/PC/ABS or PBT/PET/PC.

Preferred polymers are polyethylene,polypropylene, polystyrene, styrene block-copolymers, polybutadiene or polyisoprene, EPDM (ethylene-propylene diene monomer) or EPR (ethylene-propylene rubber).

More preferred are polyethylene, polypropylene, polybutadiene, SBS and EPDM (ethylene-propylene diene monomer).

One preferred nitroxyl radical is of formula (X)

wherein

n₁ is 0 or 1

R₁₀₁, R₁₀₂, R₁₀₃ are each independently of one another hydrogen, halogen, NO₂, cyano, —CONR₁₀₅R₁₀₆, —(R₁₀₉)COOR₁₀₄, —C(O)—R₁₀₇, —OR₁₀₈, —SR₁₀₈, —NHR₁₀₈, —N(R₁₀₈)₂, carbamoyl, di(C₁-C₁₈alkyl)carbamoyl, —C(═NR₁₀₅)(NHR₁₀₆);

unsubstituted C₁-C₁₈alkyl, C₂-C₁₈alkenyl, C₂-C₁₈alkynyl, C₇-C₉phenylalkyl, C₃-C₁₂cycloalkyl or C₃-C₁₂cycloalkyl containing at least one nitrogen or oxygen atom; or

C₁-C₁₈alkyl, C₂-C₁₈alkenyl, C₂-C₁₈ alkynyl, C₇-C₉phenylalkyl, C₃-C₁₂cycloalkyl or C₃-C₁₂cycloalkyl containing at least one nitrogen or oxygen atom, which are substituted by NO₂, halogen, amino, hydroxy, cyano, carboxy, C₁-C₄alkoxy, C₁-C₄alkylthio, C₁-C₄alkylamino or di(C₁-C₄alkyl)amino; or

phenyl, which is unsubstituted or substituted by C₁-C₄alkyl, C₁-C₄alkoxy, C₁-C₄alkylthio, halogen, cyano, hydroxy, carboxy, C₁-C₄alkylamino or di(C₁-C₄alkyl)amino;

or R₁₀₂ and R₁₀₃, together with the linking carbon atom, form a C₃-C₁₂ cycloalkyl radical, a (C₄-C₁₂ cycloalkanon)-yl radical or a C₃-C₁₂cycloalkyl radical containing at least one O atom and/or a NR₁₀₈ group; or if n₁ is 1

R₁₀₄ is hydrogen, C₁-C₁₈alkyl, phenyl, an alkali metal cation or a tetraalkylammonium cation;

R₁₀₅ and R₁₀₆ are hydrogen, C₁-C₁₈alkyl, C₂-C₁₈alkyl which is substituted by at least one hydroxy group or, taken together, form a C₂-C₁₂alkylene bridge or a C₂-C₁₂-alkylene bridge interrupted by at least one O or/and NR₁₀₈ atom;

R₁₀₇ is hydrogen, C₁-C₁₈alkyl or phenyl;

R₁₀₈ is hydrogen, C₁-C₁₈alkyl or C₂-C₁₈alkyl which is substituted by at least one hydroxy group;

R₁₀₉ is C₁-C₁₂alkylen or a direct bond;

R₁₁₀ is C₄-C₁₈alkyl bound via a tertiary C-atom to the nitrogen atom, C₉-C₁₁phenylalkyl, C₃-C₁₂cycloalkyl or C₃-C₁₂cycloalkyl containing at least one nitrogen or oxygen atom; or

C₄-C₁₈alkyl bound via a tertiary C-atom to the nitrogen atom, C₉-C₁₁phenylalkyl, C₃-C₁₂cycloalkyl or C₃-C₁₂cycloalkyl containing at least one nitrogen or oxygen atom, which are substituted by NO₂, halogen, amino, hydroxy, cyano, carboxy, C₁-C₄alkoxy, C₁-C₄alkylthio, C₁-C₄alkylamino or di(C₁-C₄alkyl)amino; or

phenyl, naphthyl, which are unsubstituted or substituted by C₁-C₄alkyl, C₁-C₄alkoxy, C₁-C₄alkylthio, halogen, cyano, hydroxy, carboxy, C₁-C₄alkylamino or di(C₁-C₄alkyl)amino;

if n₁ is 1

R₁₁₁ is C₁-C₁₈alkyl, C₇-C₉phenylalkyl, C₃-C₁₂cycloalkyl or C₃-C₁₂cycloalkyl containing at least one nitrogen or oxygen atom; or

C₁-C₁₈alkyl, C₇-C₉phenytalkyl, C₃-C₁₂cycloalkyl or C₃-C₁₂cycloalkyl containing at least one nitrogen or oxygen atom, which are substituted by NO₂, halogen, amino, hydroxy, cyano, carboxy, C₁-C₄alkoxy, C₁-C₄alkylthio, C₁-C₄alkylamino or di(C₁-C₄alkyl)amino; or

phenyl, naphthyl, which are unsubstituted or substituted by C₁-C₄alkyl, C₁-C₄alkoxy, C₁-C₄alkylthio, halogen, cyano, hydroxy, carboxy, C₁-C₄alkylamino or di(C₁-C₄alkyl)amino; or a polycyclic cycloaliphatic ring system or a polycyclic cycloaliphatic ring system with at least one di- or trivalent nitrogen atom; or

R₁₁₀ and R₁₁₁ together form a C₂-C₁₂alkylene bridge, a C₃-C₁₂alkylen-on bridge or a C₂-C₁₂alkylene bridge which is interrupted by at least one O or N atom, which bridges are unsubstituted or substituted with C₁-C₁₈alkyl, hydroxy(C₁-C₄)alkyl, phenyl, C₇-C₉phenylalkyl, NO₂, halogen, amino, hydroxy, cyano, carboxy, C₁-C₄alkoxy, C₁-C₄alkylthio, C₁-C₄alkylamino or di(C₁-C₄alkyl)amino,

R₁₁₂ is hydrogen, —(R₁₀₉)COOR₁₀₄, cyano, —OR₁₀₈, —SR₁₀₈, —NHR₁₀₈, —N(R₁₀₈)₂, —NH—C(O)—R₁₀₈, unsubstituted C₁-C₁₈alkyl, C₂-C₁₈alkenyl, C₂-C₁₈alkynyl, C₇-C₉phenylalkyl, C₃-C₁₂cycloalkyl or C₃-C₁₂cycloalkyl containing at least one nitrogen or oxygen atom; or

C₁-C₁₈alkyl, C₂-C₁₈ alkenyl, C₂-C₁₈ alkynyl, C₇-C₉phenylalkyl, C₃-C₁₂cycloalkyl or C₃-C₁₂cycloalkyl containing at least one nitrogen or oxygen atom, which are substituted by NO₂, halogen, amino, hydroxy, cyano, carboxy, C₁-C₄alkoxy, C₁-C₄alkylthio, C₁-C₄alkylamino or di(C₁-C₄alkyl)amino; or

phenyl, naphthyl, which are unsubstituted or substituted by C₁-C₄alkyl, C₁-C₄alkoxy, C₁-C₄alkylthio, halogen, cyano, hydroxy, carboxy, C₁-C₄alkylamino, di(C₁-C₄alkyl)amino; or R₁₁₁ and R₁₁₂ together with the linking carbon atom form a C₃-C₁₂cycloalkyl radical.

Another preferred nitroxyl radical is of formula XXa, XXb or XXc

wherein

Y₁ is O or CH₂;

Q is O or NR₂₂₀, wherein R₂₂₀ is hydrogen or C₁-C₁₈alkyl;

R₂₀₁ is tertiary C₄-C₁₈alkyl or phenyl, which are unsubstituted or substituted by halogen, OH, COOR₂₂₁ or C(O)—R₂₂₂ wherein R₂₂₁ is hydrogen, a alkali metal atom or C₁-C₁₈alkyl and R₂₂₂ is C₁-C₁₈alkyl; or

R₂₀₁ is C₅-C₁₂cycloalkyl, C₅-C₁₂cycloalkyl which is interrupted by at least one O or N atom, a polycyclic alkyl radical or a polycyclic alkyl radical which is interrupted by at least one O or N atom;

R₂₀₂ and R₂₀₃ are independently C₁-C₁₈alkyl, benzyl, C₅-C₁₂cycloalkyl or phenyl, which are unsubstituted or substituted by halogen, OH, COOR₂₂₁ or C(O)—R₂₂₂ or together with the carbon atom form a C₅-C₁₂cycloalkyl ring;

if Y₁ is O,

R₂₀₄ and R₂₁₂ are OH, O(alkali-metal) C₁-C₁₈alkoxy, benzyloxy, NR₂₂₃R₂₂₄, wherein R₂₂₃ and R₂₂₄ are independently from each other hydrogen, C₁-C₁₈alkyl or phenyl, which are unsubstituted or substituted by halogen, OH, COOR₂₂₁ or C(O)—R₂₂₂;

if Y₁ is CH₂,

R₂₀₄ is OH, C₁-C₁₈alkoxy, benzyloxy, O—C(O)—(C₁-C₁₈)alkyl or NR₂₂₃R₂₂₄;

R₂₁₂ are a group C(O)R₂₂₅, wherein R₂₂₅ is OH, C₁-C₁₈alkoxy, benzyloxy, NR₂₂₃R₂₂₄, wherein R₂₂₃ and R₂₂₄ are independently from each other hydrogen, C₁-C₁₈alkyl or phenyl, which are unsubstituted or substituted by halogen, OH, COOR₂₂₁ or C(O)—R₂₂₂;

R₂₀₅, R₂₀₆, R₂₀₇ and R₂₀₈ are independently of each other C₁-C₁₈alkyl, C₅-C₁₂cycloalkyl or phenyl; or

R₂₀₅ and R₂₀₆ and/or R₂₀₇ and R₂₀₈ together with the carbon atom form a C₅-C₁₂cycloalkyl ring;

R₂₀₉ and R₂₁₀ are independently of each other hydrogen, formyl, C₂-C₁₈alkylcarbonyl, benzoyl, C₁-C₁₈alkyl, C₅-C₁₂cycloalkyl, C₅-C₁₂cycloalkyl which is interrupted by at least one O or N atom, benzyl or phenyl which are unsubstituted or substituted by halogen, OH, COOR₂₂₁ or C(O)—R₂₂₂;

R₂₁₁, is formyl, C₂-C₁₈alkylcarbonyl, benzoyl, C₁-C₁₈alkyl, C₅-C₁₂cycloalkyl, C₅-C₁₂cycloalkyl which is interrupted by at least one O or N atom, benzyl or phenyl which are unsubstituted or substituted by halogen, OH, COOR₂₂₁ or C(O)—R₂₂₂.

Still another preferred nitroxyl radical contains a structural element of formula (XXX)

G₁, G₂, G₃, G₄ are independently C₁-C₆alkyl or G₁ and G₂ or G₃ and G₄, or G₁ and G₂ and G₃ and G₄ together form a C₅-C₁₂cycloalkyl group;

G₅, G₆ independently are H, C₁-C₁₈alkyl, phenyl, naphthyl or a group COOC₁-C₁₈alkyl.

More preferred is a nitroxyl radical, wherein the structural element of formula (XXX) is any of formulae A to S

wherein

G₁, G₂, G₃ and G₄ are independently alkyl of 1 to 4 carbon atoms, or G₁ and G₂ together and G₃ and G₄ together, or G₁and G₂ together or G₃ and G₄ together are pentamethylene;

G₅ and G₆ are independently hydrogen or C₁-C₄ alkyl;

R, if m is 1, is hydrogen, C₁-C₁₈alkyl which is uninterrupted or interrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic carboxylic acid having 2 to 18 carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or an α,β-unsaturated carboxylic acid having 3 to 5 carbon atoms or of an aromatic carboxylic acid having 7 to 15 carbon atoms, where each carboxylic acid can be substituted in the aliphatic, cycloaliphatic or aromatic moiety by 1 to 3 —COOZ₁₂ groups, in which Z₁₂ is H, C₁-C₂₀alkyl, C₃-C₁₂alkenyl, C₅-C₇cycloalkyl, phenyl or benzyl; or

R is a monovalent radical of a carbamic acid or phosphorus-containing acid or a monovalent silyl radical;

R, if m is 2, is C₂-C₁₂alkylene, C₄-C₁₂alkenylene, xylylene, a divalent radical of an aliphatic dicarboxylic acid having 2 to 36 carbon atoms, or a cycloaliphatic or aromatic dicarboxylic acid having 8-14 carbon atoms or of an aliphatic, cycloaliphatic or aromatic dicarbamic acid having 8-14 carbon atoms, where each dicarboxylic acid may be substituted in the aliphatic, cycloaliphatic or aromatic moiety by one or two —COOZ₁₂ groups; or

R is a divalent radical of a phosphorus-containing acid or a divalent silyl radical;

R, if m is 3, is a trivalent radical of an aliphatic, cycloaliphatic or aromatic tricarboxylic acid, which may be substituted in the aliphatic, cycloaliphatic or aromatic moiety by —COOZ₁₂, of an aromatic tricarbamic acid or of a phosphorus-containing acid, or is a trivalent silyl radical,

R, if m is 4, is a tetravalent radical of an aliphatic, cycloaliphatic or aromatic tetracarboxylic acid;

p is 1, 2 or 3,

R₁ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl;

when p is 1,

R₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl, C₂-C₈alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, or is glycidyl, a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z— or —CONH—Z wherein Z is hydrogen, methyl or phenyl; or

when p is 2,

R₂ is C₂-C₁₂alkylene, C₆-C₁₂-arylene, xylylene, a —CH₂CH(OH)CH₂—O—B—O—CH₂CH(OH)CH₂— group, wherein B is C₂-C₁₀alkylene, C₆-C₁₅arylene or C₆-C₁₂cycloalkylene; or, provided that R₁ is not alkanoyl, alkenoyl or benzoyl, R₂ can also be a divalent acyl radical of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid or dicarbamic acid, or can be the group —CO—; or R₁ and R₂ together when p is 1 can be the cyclic acyl radical of an aliphatic or aromatic 1,2- or 1,3-dicarboxylic acid; or

R₂ is a group

where T₇ and T₈ are independently hydrogen, alkyl of 1 to 18 carbon atoms, or T₇ and T₈ together are alkylene of 4 to 6 carbon atoms or 3-oxapentamethylene;

when p is 3,

R₂ is 2,4,6-triazinyl;

when n is 1,

R₃ is C₂-C₈alkylene or hydroxyalkylene or C₄-C₂₂acyloxyalkylene; or

when n is 2,

R₃ is (—CH₂)₂C(CH₂—)₂;

when n is 1,

R₄ is hydrogen, C₁-C₁₂alkyl, C₃-C₅alkenyl, C₇-C₉aralkyl, C₅-C₇cycloalkyl, C₂-C₄hydroxyalkyl, C₂-C₆-alkoxyalkyl, C₆-C₁₀-aryl, glycidyl, a group of formula —(CH₂)_(m)—COO—Q or of the formula —(CH₂)_(m)—O—CO—Q wherein m is 1 or 2 and Q is C₁-C₄-alkyl or phenyl; or

when n is 2,

R₄ is C₂-C₁₂alkylene, C₆-C₁₂-arylene, a group —CH₂CH(OH)CH₂—O—D—O—CH₂CH(OH)CH₂— wherein D is C₂-C₁₀alkylene, C₆-C₁₅arylene or C₆-C₁₂cycloalkylene, or a group —CH₂CH(OZ₁)CH₂—(OCH₂CH(OZ₁)CH₂)₂— wherein Z₁ is hydrogen, C₁-C₁₈alkyl, allyl, benzyl, C₂-C₁₂alkanoyl or benzoyl;

R₅ is hydrogen, C₁-C₁₂alkyl, allyl, benzyl, glycidyl or C₂-C₆alkoxyalkyl;

Q₁ is —N(R₇)— or —O—;

E is C₁-C₃alkylene, the group —CH₂CH(R₈)—O— wherein R₈ is hydrogen, methyl or phenyl, the group —(CH₂)₃—NH— or a direct bond;.

R₇ is C₁-C₁₈alkyl, C₅-C₇-ycloalkyl, C₇-C₁₂aralkyl, cyanoethyl, C₆-C₁₀aryl, the group —CH₂CH(R₈)—OH; or a group of the formula

or a group of the formula

wherein

G is C₂-C₆alkylene or C₆-C₁₂arylene and R is as defined above; or

R₇ is a group —E—CO—NH—CH₂-OR₆;

R₆ is hydrogen or C₁-C₁₈alkyl;

Formula (F) denotes a recurring structural unit of a oligomer where T is ethylene or 1,2-propylene, or is a repeating structural unit derived from an α-olefin copolymer with an alkyl acrylate or methacrylate;

k is 2to 100;

and R₁₀ is hydrogen, C₁-C₁₂alkyl or C₁-C₁₂alkoxy;

T₂ has the same meaning as R₄;

T₃ and T₄ are independently alkylene of 2 to 12 carbon atoms, or T₄ is a group

T₃ is C₂-C₂₂alkylene, C₅-C₇cycloalkylene, C₁-C₄alkylenedi(C₅-C₇cycloalkylene), phenylene or phenylenedi(C₁-C₄alkylene);

where

a, b and c are independently 2 or 3, and d is 0 or 1;

e is 3 or 4;

E₁ and E₂ being different, are each oxo or imino;

E₃ is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl, said phenyl or said naphthyl substituted by chlorine or by alkyl of 1 to 4 carbon atoms, or phenylalkyl of 7 to 12 carbon atoms, or said phenylalkyl substituted by alkyl of 1 to 4 carbon atoms;

E₄ is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl or phenylalkyl of 7 to 12 carbon atoms; or

E₃ and E₄ together are polymethylene of 4 to 17 carbon atoms, or said polymethylene substituted by up to four alkyl groups of 1 to 4 carbon atoms; and

E₆ is an aliphatic or aromatic or aromatic tetravalent radical.

Further suitable heterocyclic NO. radicals are for example mentioned in WO 98/30601 or in WO 98/44008, which are incorporated by reference.

Alkyl with up to 20 carbon atoms is, for example, methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl. The alkyl groups may be linear or branched.

C₃-C₁₈alkyl which is interrupted by one or more oxygen atoms is preferably derived from ethylene oxide or propylene oxide.

C₃-C₁₈alkyl interrupted by at least one O atom is for example —CH₂—CH₂—O—CH₂—CH₃, —CH₂—CH₂—O—CH₃ or —CH₂—CH₂—Q—CH₂—CH₂—CH₂—O—CH₂—CH₃. It is preferably derived from polyethylene glycol. A general description is —((CH₂)_(a)—O)_(b)—H/CH₃, wherein a is a number from 1 to 6 and b is a number from 2 to 10.

C₃-C₁₂alkenyl is linear or branched and for example propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, dodecenyl including their isomers.

C₃-C₈alkynyl is preferably propargyl.

C₅-C₁₂cycloalkyl is typically, cyclopentyl, methylcyclopentyl, dimethylcyclopentyl, cyclohexyl, methylcyclohexyl.

Cycloalkyl which is interrupted by at least one O or N atom is for example 2-tetrahydropyran-yl, tetrahydrofurane-yl, 1,4 dioxan-yl, pyrrolidin-yl, tetrahydrothiophen-yl, pyrazolidin-yl, imidazolidin-yl, butyrolactone-yl, caprolactame-yl

Examples for alkali metal are lithium, sodium or potassium.

Alkyl substituted by —OH is typically 2-hydroxyethyl, 2-hydroxypropyl or 2-hydroxybutyl.

C₁-C₁₈alkoxy is, for example, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, pentoxy, isopentoxy, hexoxy, heptoxy, octoxy, decyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy and octadecyloxy.

C₁-C₁₈Alkyl substituted by C₁-C₈alkoxy, preferably by C₁-C₄alkoxy, in particular by methoxy or ethoxy, is typically 2-methoxyethyl, 2-ethoxyethyl, 3-methoxypropyl, 3-ethoxypropyl, 3-butoxypropyl, 3-octoxypropyl and 4-methoxybutyl.

C₁-C₁₈Alkyl substituted by di(C₁-C₄alkyl)amino is preferably e.g. dimethylamino, diethylamino, 2-dimethylaminoethyl, 2-diethylaminoethyl, 3-dimethylaminopropyl, 3-diethylaminopropyl, 3-dibutylaminopropyl and 4-diethylaminobutyl.

C₁-C₁₈Alkyl substituted by C₁-C₄alkylamino is preferably e.g. methylamino, ethylamino, 2-methylaminoethyl, 2-ethylaminoethyl, 3-methylaminopropyl, 3-ethylaminopropyl, 3-butylamino-propyl and 4-ethylaminobutyl.

C₁-C₄Alkylthio is typically thiomethyl, thioethyl, thiopropyl, thioisopropyl, thiobutyl and thioisobutyl.

C₂-C₁₈ alkylcarbonyl is for example acetyl, propionyl, butyryl, pentylcarbonyl, hexylcarbonyl or dodecylcarbonyl.

C₇-C₉phenylalkyl or C₇-C₉aralkyl is for example benzyl, phenylethyl, phenylpropyl, α,α-dimethylbenzyl or α-methylbenzyl.

Examples of C₂-C₁₂alkylene bridges, preferably of C₂-C₆alkylene bridges, are ethylene, propylene, butylene, pentylene, hexylene.

C₂-C₁₂alkylene bridges interrupted by at least one N or O atom are, for example, —CH₂—O—CH₂—CH₂, —CH₂—O—CH₂—CH₂—CH₂, —CH₂—O—CH₂—CH₂—CH₂—CH₂—, —CH₂—O—CH₂—CH₂—O—CH2-, —CH₂—NH—CH₂—CH₂, —CH₂—NH—CH₂—CH₂—CH₂, —CH₂—NH—CH₂—CH₂—CH₂—CH2-, —CH₂—NH—CH₂—CH₂—NH—CH₂— or —CH₂—NH—CH₂—CH₂—O—CH2-,

Examples for C₄-C₁₂cycloalkanone-yl are cyclopentanone-yl, cyclohexanone-yl or cycloheptanone-yl.

Phenyl substituted by 1, 2 or 3 C₁-C₄alkyl or C₁-C₄alkoxy is typically methylphenyl, dimethyl-phenyl, trimethylphenyl, t-butylphenyl, di-t-butylphenyl, 3,5-di-t-butyl-4-methylphenyl, methoxyphenyl, ethoxyphenyl and butoxyphenyl.

Examples of polycyclic cycloaliphatic ring systems are adamantane, cubane, twistane, norbornane, bycyclo[2.2.2]octane or bycyclo[3.2.1]octane.

An example of a polycyclic heterocycloaliphatic ring system is hexamethylentetramine (urotropine).

Examples of monocarboxylic acids with 1 to 18 carbon atoms are formic acid, acetic acid, propionic acid, phenyl acetic acid, cyclohexane carbonic acid, mono-, di- and trichlor-acetic acid or mono-, di- and trifluor-acetic acid. Other suitable acids are benzoic acid, chlor-benzoic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, chlorbenzenesulfonic acid, trifluormethanesulfonic acid, methylphosphonic acid or phenylphosphonic acid.

Examples of a monovalent radical of a carboxylic acid are an acetyl, caproyl, stearoyl, acryloyl, methacryloyl, cyclohexylcarboxylic acid, benzoyl or β-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionyl radical.

Further examples are derived from propionic acid, laurinic acid or methyl ethyl acetic acid or the other isomers of valeric acid.

Examples of a cycloaliphatic carboxylic acid is for example cyclohexane carboxylic acid or cyclopentane carboxylic acid.

An example of an aromatic carboxylic acid is benzoic acid.

Typical unsaturated carboxylic acids are acrylic acid, methacrylic acid or crotonic acid.

Examples of a monovalent silyl radical are of the formula —(C_(j)H_(2j))—Si(Z′)₂Z″, in which j is an integer in the range from 2 to 5. and Z′ and Z″, independently of one another, are C₁-C₄alkyl or C₁-C₄alkoxy.

Examples of di-, tri- and tetra valent acids are for example malonyl, succinyl, glutaryl, adipoyl, suberoyl, sebacoyl, maleoyl, itaconyl, phthaloyl, dibutylmalonyl, dibenzylmalonyl, butyl(3,5-di-tert-butyl-4-hydroxybenzyl)malonyl or bicycloheptenedicarbonyl radical or a group of the formula

trimellitoyl, citryl or nitrilotriacetyl, butane-1,2,3,4-tetracarboxylic acid or pyromellitic acid.

Examples of a dicarbamic acid are the hexamethylenedicarbamoyl or 2,4-toluylenedicarbamoyl radicals.

C₂-C₁₂alkanoyl is, for example, propionyl, butyryl, octanoyl, dodecanoyl, but preferably acetyl.

Hydroxyl-, cyano-, alkoxycarbonyl- or carbamide-substituted alkyl can be, for example, 2-hydroxyethyl, 2-hydroxypropyl, 2-cyanoethyl, methoxycarbonyimethyl, 2-ethoxycarbonylethyl, 2-aminocarbonylpropyl or 2-(dimethylaminocarbonyl)ethyl.

Any C₂-C₁₂alkylene radicals are, for example, ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene, decamethylene or dodecamethylene.

C₄-C₁₂alkenylene is for example butenylene, pentenylene, hexenylene, heptenylene or nonenylene including their isomers.

C₆-C₁₂arylene is, for example, o-, m- or p-phenylene, 1,4-naphthylene or 4,4′-diphenylene.

C₄-C₂₂acyloxyalkylene is, for example, 2-ethyl-2-acetoxymethylpropylene. Any C₂-C₆alkoxyalkyl substituents are, for example, methoxymethyl, ethoxymethyl, propoxymethyl, tert-butoxymethyl, ethoxyethyl, ethoxypropyl, n-butoxyethyl, tert-butoxyethyl, isopropoxyethyl or propoxypropyl.

C₁-C₁₈alkanoyloxy is, for example, formyloxy, acetyloxy, propionyloxy, butyryloxy, valeryloxy, lauroyloxy, palmitoyloxy and stearoyloxy.

The nitroxyl radicals of formula (X) are known and may be prepared according to WO 99/03984, EP-A-0 891 986 or WO 98/13392.

Some typical examples are given below.

The nitroxyl radicals of formula XXa, b and c are also known and may be prepared according to European Patent Application No. 98810741.3.

Typical examples are given below.

The nitroxyl radicals of formula XXX are also known and can be prepared as described in European Patent Application No. 98810531.8.

Furthermore DE 26 21 841, U.S. Pat. No. 4,131,599 and DE 26 30 798 for example describe the preparation of 2,6-diethyl-2,3,6-trimethyl-4-oxopiperidine and 2,6-dipropyl-3-ethyl-2,6-dimethyl-4-oxo-piperidine, which are intermediates for the corresponding 1-oxo compounds.

Another method for the preparation of 2,2-dimethyl-6,6-dialkyl-4-oxopiperidine is described by F. Asinger, M. Thiel, H. Baltz, Monatshefte fucr Chemie 88, 464 (1957) or by J. Bobbittt et al. in J. Org. Chem. 58, 4837 (1993).

The oxidation of the piperidine compound to 1-oxo-piperidine derivatives is well known in the art and for example described by L. B. Volodarsky, V. A. Reznikov, V. I. Ovcharenko in Synthetic Chemistry of Stable Nitroxides, CRC Press, Boca Raton 1994.

The tetramethylpiperidine precursors are partially commercially available or can be prepared according to known methods. For example U.S. Pat. No. 5,096,950 and the documents cited therein describe the preparation of the precursors. The oxidation process can be done as described above.

Examples are given below.

Preferably G₁, G₂, G₃ and G₄ are methyl or ethyl and G₅ and G₆ are hydrogen or methyl.

More preferably G₁, G₂, G₃ and G₄ are methyl and G₅ and G₆ are hydrogen.

Another preferred group of compounds are those wherein G₁ and G₃ are ethyl and G₂ and G₄ are methyl, or G₁ and G₄ are ethyl and G₂ and G₃ are methyl, and one of G₅ or G₆ is hydrogen and the other methyl or both are hydrogen.

A preferred subgroup are compounds of the structural formulae A, B, O or P, wherein

m is 1,

R is hydrogen, C₁-C₁₈alkyl which is uninterrupted or interrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic carboxylic acid having 2 to 18 carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or an α,β-unsaturated carboxylic acid having 3 to 5 carbon atoms or of an aromatic carboxylic acid having 7 to 15 carbon atoms;

p is 1;

R₁ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl;

R₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl, C₂-C₈alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, or is glycidyl, a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z or —CONH—Z wherein Z is hydrogen, methyl or phenyl.

More preferred are those of structure A or B.

Preferably R is hydrogen, C₁-C₁₈alkyl, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic carboxylic acid, having 2 to 18 carbon atoms;

R₁ is C₁-C₁₂alkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl;

R₂ is C₁-C₁₈alkyl, glycidyl, a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z, wherein Z is hydrogen, methyl or phenyl.

Another preferred subgroup is wherein the stable nitroxyl radical is a compound of formula (X),

n, is 1

R₁₀₁ is cyano;

R₁₀₂ and R₁₀₃, are each independently of one another unsubstituted C₁-C₁₂alkyl or phenyl;

or R₁₀₂ and R₁₀₃, together with the linking carbon atom, form a C₅-C₇ cycloalkyl radical;

R₁₁₀ is C₄-C₁₂alkyl bound via a tertiary C-atom to the nitrogen atom, C₉-C₁₁phenylalkyl or phenyl; or

R₁₁₀ and R₁₁₁ together form a C₂-C₆alkylene bridge which is unsubstituted or substituted with C₁-C₄alkyl; and

R₁₁₂ is C₁-C₄alkyl.

A further preferred subgroup is wherein the stable nitroxyl radical is a compound of formula (XXa),

Y is O;

R₂₀₁ is tertiary C₄-C₈alkyl;

R₂₀₂ and R₂₀₃ are methyl, ethyl or together with the carbon atom form a C₅-C₆cycloalkyl ring;

R₂₀₄ is C₁-C₁₈alkoxy, benzyloxy or NR₂₂₃R₂₂₄, wherein R₂₂₃ and R₂₂₄ are independently of each other hydrogen or C₁-C₈alkyl;

or of formula (XXb), wherein Q₁ is O;

R₂₀₅, R₂₀₆, or, R₂₀₇ and R₂₀₈ are independently of each other methyl or ethyl; or

R₂₀₅ and R₂₀₆ and/or R₂₀₇ and R₂₀₈ together with the carbon atom form a C₅-C₆cycloalkyl ring;

R₂₀₉ and R₂₁₀ are independently of each other formyl, C₂-C₈alkylcarbonyl, benzoyl, C₁-C₈alkyl,

benzyl or phenyl;

or of formula (XXc), wherein Y₁ is O;

R₂₀₅, R₂₀₆, R₂₀₇ and R₂₀₈ are independently of each other methyl or ethyl; or

R₂₀₅ and R₂₀₆ and/or R₂₀₇ and R₂₀₈ together with the carbon atom form a C₅-C₆cycloalkyl ring;

R₂₁₁ is formyl, C₂-C₁₈alkylcarbonyl, benzoyl, C₁-C₁₈alkyl, benzyl or phenyl and

R₂₁₂ is OH, C₁-C₁₈alkoxy, benzyloxy, NR₂₂₃R₂₂₄, wherein R₂₂₃ and R₂₂₄ are independently of each other hydrogen or C₁-C₁₈alkyl.

Preferably the polymer to be. grafted on contains unsaturated moieties selected from the group consisting of polydienes, co-, block-, random- and tapered polymers of styrene, terpolymers with diolefins and copolymers with diolefins.

Preferred unsaturated polymers are polybutadiene, polyisoprene, styrene-isoprene-block-copolymers (SI, SIS), styrene-butadiene-block-copolymers (SB, SBS, SEBS), ABS, EPDM, butyl rubber, chloroprene rubber and nitrile rubber having a content of unsaturated repeating units from 0.1 to 85%. Mostly preferred are SB, SBS, EPDM having a content of unsaturated repeating units from 1 to 70%.

Preferably the ethylenically unsaturated monomer or oligomer is selected from the group consisting of styrene, substituted styrene, conjugated dienes, maleic acid anhydride, acrolein, vinyl acetate, (alkyl)acrylic acidanhydrides, (alkyl)acrylic acid salts, (alkyl)acrylic esters or (alkyl)acrylamides.

More preferably the ethylenically unsaturated monomer is styrene, α-methyl styrene, p-methyl styrene or a compound of formula CH₂═C(R_(a))—(C═Z)—R_(b), wherein R_(a) is hydrogen or C₁-C₄alkyl, R_(b) is NH₂, OCH₃, glycidyl, unsubstituted C₁-C₁₈alkoxy or hydroxy-substituted C₁-C₁₈alkoxy, unsubstituted C₁-C₁₈alkylamino, di(C₁-C₁₈alkyl)amino, hydroxy-substituted C₁-C₁₈alkylamino or hydroxy-substituted di(C₁-C₁₈alkyl)amino;

Me is a monovalent metal atom

Z is oxygen or sulfur.

Most preferably R_(a) is hydrogen or methyl, R_(b) is NH₂, gycidyl, unsubstituted or with hydroxy substituted C₁-C₄alkoxy, unsubstituted C₁-C₄alkylamino, di(C₁-C₄alkyl)amino, hydroxy-substituted C₁-C₄alkylamino or hydroxy-substituted di(C₁-C₄alkyl)amino;and

Z is oxygen.

Specifically preferred ethylenically unsaturated monomers are methylacrylate, ethylacrylate, butylacrylate, isobutylacrylate, tert. butylacrylate, hydroxyethylacrylate, hydroxypropylacrylate, dimethylaminoethylacrylate, glycidylacrylates, methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, dimethylaminoethyl(meth)acrylate, glycidyl(meth)acrylates, acrylonitriie, acrylamide or methacrylamide.

The temperature applied in the first reaction step depends on the polymer and is for example 50° to 150° C. above the glass transition temperature (Tg) for amorphous polymers and 20° to 180° C. above the melting temperature (Tm) for semi-crystalline polymers. Typical are following temperatures:

low density polyethylene LDPE 170-260° C. high density polyethylene HDPE 180-270° C. polypropylene PP 180-280° C. polystyrene PS 190-280° C. styrene-block copolymers SB(S) 180-260° C. ethylene-propylene-diene modified EPDM 180-260° C. ethylene propylene rubber EPR 180-260° C.

In a preferred process the temperature in the first step A) is from 150° C. to 300° C., more preferred from 170° C. to 280° C.

Preferably the temperature in the second step B) is from 70° to 280° C., more preferably from 70° to 210° C.

Preferably the stable nitroxyl radical is present in an amount from 0.1% to 30%, more preferably in an amount from 0.1% to 20% and most preferably in an amount from 0.5% to 10% based on the weight of the polymer.

Preferably the weight ratio of the reaction product of step A) to the ethylenically unsaturated monomer or oligomer added in step B) is from 1:1000 to 10:1, more preferably from 1:100 to 1:1 and most preferably from 1:50 to 1:1.

Step A) of the process may be performed in any reactor suitable for mixing a polymer melt. Preferably the reactor is an extruder or kneading apparatus as for example described in “Handbuch der Kunststoffextrusion” Vol. I, editor F. Hensen, W. Knappe and H. Potente, 1989, pages 3-7. If an extruder is used the process may be described as reactive extrusion process. Examples of reactive extrusion equipment and processes are given by G. H. Hu et al., in “Reactive Modifiers for Polymers”, first edition, Blackie Academic & Professional an Imprint of Chapman & Hall, London 1997, chapter 1, pages 1-97.

Preferably, if an extruder is used, a reduced pressure of less than 200 mbar is applied during extrusion. Volatile by products may be removed thereby.

The reaction time for step A) depends on the desired amount of grafted ONR′R″ initiator moieties. Typical reaction times are from a few minutes to an hour. Preferably the reaction time is from 1 min to 1 h, most preferably from 2 min to 20 min.

The reaction step B) may be performed immediately after step A), however it is also possible to store the intermediate polymeric radical initiator at room temperature for some time. The intermediate polymeric radical initiator is stable at room temperature and no loss of activity occurs up to several months.

The reaction step B) may be performed in any reactor suitable for mixing a polymer melt with a monomer. It is also possible to dissolve or disperse the polymer and to add the monomer to the solution. The process B) may thus optionally be performed in solution.

The degree of grafting depends on the reaction time, on the temperature used and the activity of the polymeric initiator. Preferably the reaction time for step B) is from 1 min to 20 hours, more preferably from 30 min to 5 hours.

If the reaction step B) is performed in an extruder, a reaction time of 2 to 20 minutes is preferred.

The grafted polymers are useful in many applications such as compatibilizers in polymer blends or alloys, adhesion promoters between two different substrates, surface modification agents, nucleating agents, coupling agents between filler and polymer matrix or dispersing agents.

The process is particularly useful for the preparation of grafted block copolymers.

Grafted block copolymers are, for example, grafted block copolymers of polystyrene and polyacrylate (e.g., poly(styrene-co-acrylate) or poly(styrene-co-acrylate-co-styrene). They are useful as adhesives or as compatibilizers for polymer blends or as polymer toughening agents. Poly(methylmethacrylate-co-acrylate) diblock graft copolymers or poly(methylacrylate-co-acrylate-co-methacrylate) triblock graft copolymers are useful as dispersing agents for coating systems, as coating additives (e.g. rheological agents, compatibilizers, reactive diluents) or as resin component in coatings(e.g. high solid paints). Graft block copolymers of styrene, (meth)acrylates and/or acrylonitrile are useful for plastics, elastomers and adhesives.

Furthermore, graft block copolymers of this invention, wherein the grafted blocks have polar monomers on a non polar polymer are useful in many applications as amphiphilic surfactants or dispersants for preparing highly uniform polymer blends.

Thus, the present invention also encompasses in the synthesis novel graft block, multi-block, star, gradient, random, hyperbranched and dendritic copolymers.

The polymers prepared by the present invention are particularly useful for following applications: adhesives, detergents, dispersants, emulsifiers, surfactants, defoamers, adhesion promoters, corrosion inhibitors, viscosity improvers, lubricants, rheology modifiers, thickeners, crosslinkers, paper treatment, water treatment, electronic materials, paints, coatings, photography, ink materials, imaging materials, superabsorbants, cosmetics, hair products, preservatives, biocide materials or modifiers for asphalt, leather, textiles, ceramics and wood.

Because the present graft polymerization is a “living” polymerization, it can be started and stopped practically at will. Furthermore, the polymer product retains the functional alkoxyamine group allowing a continuation of the polymerization in a living matter. Thus, in one embodiment of this invention, once the first monomer is consumed in the initial polymerizing step a second monomer can then be added to form a second block on the growing graft polymer chain in a second polymerization step. Therefore it is possible to carry out additional graft polymerizations with the same or different monomer(s) to prepare multi-block graft copolymers.

Furthermore, since this is a living radical polymerization, graft blocks can be prepared in essentially any order.

Consequently further subjects of the present invention are a polymeric radical initiator prepared according to step A) of the process without an additional free radical source and a polymeric radical initiator prepared according to step A) of the process with an additional free radical source.

The polymeric radical initiator obtainable by step A) of the above process is schematically represented in formula (P1)

R₄₉₈ is hydrogen, substituted or unsubstituted C₁-C₁₈alkyl, C₂-C₁₈alkenyl, C₂-C₁₈alkinyl; C₃-C₂₀cycloalkyl or C₃-C₁₂cycloalkyl containing at least one nitrogen or oxygen atom or C₃-C₁₂cycloalkyl containing at least one nitrogen or oxygen atom, which are substituted by NO₂, halogen, amino, hydroxy, cyano, carboxy; C₁-C₄alkoxy, C₁-C₄alkylthio, C₁-C₄alkylamino or di(C₁-C₄alkyl)amino, O(C₁-C₁₈alkyl), O(C₂-C₁₈alkeny), C₇-C₁₁phenylalkyl, O-phenyl, OC₇-C₉phenylalkyl or halogen or phenyl and naphthyl which are unsubstituted or substituted by C₁-C₄alkyl, C₁-C₄alkoxy, C₁-C₄alkylthio, halogen, cyano, hydroxy, carboxy, C₁-C₄alkylamino or di(C₁-C₄alkyl)amino;

R₄₉₉ is the stable nitroxyl radical, bound at the oxygen atom;

R₅₀₀ is substituted or unsubstituted C₁-C₁₈alkyl, C₂-C₁₈alkenyl, C₃-C₂₀cycloalkyl, phenyl, C₇-C₁₁phenylalkyl;

R₅₀₁ is hydrogen, substituted or unsubstituted C₁-C₁₈alkyl, C₂-C₁₈alkenyl, C₂-C₁₈alkinyl, C₃-C₂₀cycloalkyl, phenyl, O(C₁-C₁₈alkyl), O(C₂-C₁₈alkeny), C₇-C₁₁phenylalkyl, O-phenyl, O—C₇-C₉phenylalkyl or halogen, CN, COOR₅₀₀, CONR₅₀₀R₅₀₀;

Q₅ is CR₅₀₂R₅₀₃, CH═CH₂, (CR₅₀₂R₅₀₃)_(n), CR₅₀₄═CR₅₀₅-CR₅₀₆R₅₀₇, (CR₅₀₄═CR₅₀₅-CR₅₀₆R₅₀₇)_(n), C≡CR₅₀₈R₅₀₉, (C≡CR₅₀₈R₅₀₉)_(n), O, C═O, NR₅₁₀, NR₅₁₁—C═O, O—C(O)—O, SO₂, S, SiR₅₁₂R₅₁₃, O—SiR₅₁₂R₅₁₃ 13 O;

R₅₀₂, R₅₀₃, R₅₀₄, R₅₀₅, R₅₀₆, R₅₀₇, R₅₀₈, R₅₀₉, R₅₁₀, R₅₁₁, R₅₁₂ and R₅₁₃ independently of each other are hydrogen, substituted or unsubstituted C₁-C₁₈alkyl, C₂-C₁₈alkenyl, C₂-C₁₈alkinyl, C₃-C₇cycloalkyl, phenyl, O(C₁-C₁₈alkyl), O(C₂-C₁₈alkeny), C₇-C₁₁phenylalkyl, O-phenyl, O—C₇-C₉phenylalkyl or halogen;

n is a number from 1 to 10;

y is a number from 1 to 25000 and;

z is a number from 0 to 25000.

Preferably R₅₀₁ is H or methyl; Q₅ is CR₅₀₂R₅₀₃, CH═CH₂, CR₅₀₄═CR₅₀₅CR₅₀₆CR₅₀₇, wherein R₅₀₂ and R₅₀₃ is H, methyl or C₂-C₉alkenyl and R₅₀₄, R₅₀₅, R₅₀₆ and R₅₀₇ are independently H or methyl.

Examples for the different substituents have been already given.

Within this selection polyethylene, polypropylene and polybutadiene, SBS and EPDM are especially preferred.

A further subject of the invention is a polymer of formula (P2) obtainable by step B) of the above process.

Definitions and examples of the substituents are as given above; Q₆ is a homo-, co- or tapered polymer resulting from the monomers as described above, t is a number from 0 to 25000.

R₄₉₉ may be removed thermally or chemically.

Preferably the polymer (P2) is grafted with a monomer selected from the groups described above and more preferably with styrenes, (meth)acrylates, butadiene, isoprene.

Most preferred are SB-g-styrenes, SB-g-(meth)acrylates, SI-g-styrenes, SI-g-(meth)acrylates, SBS-g-styrenes, SBS-g-(meth)acrylates, EPDM-g-styrenes, EPDM-g-(meth)acrylates.

Still a further subject is a polymer obtainable by step A) and B) of the process as defined above.

Yet another subject of the present invention is a composition comprising

a) a polymeric radical initiator prepared according to step A) as defined above optionally the preparation being done in the presence of a free radical source and

b) an ethylenically unsaturated monomer or oligomer.

Examples for the different substituents and their preferences are already given, they apply also for the other subjects of the invention.

Further subjects are the use of a stable nitroxyl radical for the preparation of a grafted polymer as defined above and the use of a grafted polymer according to step A) as defined above, as macroinitiator for radical polymerization.

Also subject of the present invention is the use of the polymer prepared according to the process as defined above, as adhesive or compatibilizer for polymer blends or as polymer toughening agents.

Poly(methylmethacrylate-co-acrylate) diblock graft copolymers or poly(methylacrylate-co-acrylate-co-methacrylate) triblock graft copolymers are useful as dispersing agents for coating systems, as coating additives (e.g. Theological agents, compatibilizers, reactive diluents) or as resin component in coatings(e.g. high solid paints). Graft block copolymers of styrene, (meth)acrylates and/or acrylonitrile are useful for plastics, elastomers and adhesives.

Furthermore, graft block copolymers of this invention, wherein the grafted blocks have polar monomers on a non polar polymer are useful in many applications as amphiphilic surfactants or dispersants for. preparing highly uniform polymer blends.

The following examples illustrate the invention.

A) Grafting of R′R″N—O* to the Polymer (Preparation of a Polymeric Initiator)

In a Brabender mixer chamber W50 (40 rpm) heated to 180-220° C., 36.6 g of a commercially available polypropylene (MFR_(230/2.16)=1.43 according to ISO 1133) are kneaded under N₂ for 10 min. The additives (Table 1) are introduced into the mixer chamber right at the beginning, together with the polypropylene. After 10 min the mixing is stopped. The polymer material is removed from the mixer chamber, compression molded at 30° C. at about 50 kN for 1 min and comminuted into granules. The granulated polymer is dissolved, reprecipitated and high temperature NMR spectra are taken to determine whether polymer bound NO-moieties are present.

TABLE 1 Grafting of R′R″N—O* to polypropylene Processing temperature Polymer bound NO Example Additives [° C.] [%] A1 4.0% compound 1 180 2.2 4.0% peroxide 1 A2 4.0% compound 1 200 2.0 4.0% peroxide 1 A3 4.0% compound 1 220 1.0 4.0% peroxide 1 A4 4.0% compound 2 180 1.6 6.0% peroxide 1 A5 4.0% compound 2 200 1.5 6.0% peroxide 1 A6 4.0% compound 2 220 1.1 6.0% peroxide 1 compound 1: benzoic acid 2,2,6,6-tetramethyl-piperidin-1-oxyl-4-yl ester compound 2: 4-hydroy-2,2,6,6-tetramethyl-piperidin-1-oxyl peroxide 1: dicumylperoxide

B) Grafting of R′R″N—O* to the Polymer and Subsequent Polymernalogous Reaction

Commercially available polymers (SBS=styrene/butadiene/styrene copolymer, Kraton D 1102 CU, supplier: Shell; SEBS=styrene/ethylene/butadiene/styrene copolymer Kraton G 1652, supplier: Shell; EPDM=ethylene/propylene/ethylidenenorbornene terpolymer, Buna EP G 3850, supplier: Bayer) are extruded together with the compounds given in Table 2 in a twin screw extruder (TW 100 of Haake, Germany) at 180-210° C. (heating zones 1-5) and 40 rpm. In an evacuated Schienk reactor, purged with argon, 5 g of the granulated polymer is dissolved in 50-100 mL monomer under argon atmosphere. Dissolved oxygen is removed in freeze-thaw-cycles (liquid nitrogen). The reaction mixture is stirred and heated under argon atmosphere. Remaining monomer is removed under vacuum and the residue is dried under vacuum until constant weight is achieved. Molecular weights and molecular weight distributions are determined by gel permeation chromatograpgy (GPC). The results are shown in Table 3.

TABLE 2 Grafting of R′R″N—O* to the polymer Poly- Molecular dispersity Polymer weight (Mn, (Mw/Mn, Example type Additives GPC) GPC) Comparison 1 SBS not processed 105.500* A7 Starting mate- SBS 1.0% compound 104.200* rial for inventive 3 example 1 A8 Starting mate- SBS 0.5% compound 103.100* rial for inventive 4 example 2 Comparison 2 EPDM not processed 96.300 2.41 A9 Starting mate- EPDM 0.5% compound 87.400 3.25 rial for inventive 4 example 3 A10 Starting EPDM 1.0% compound 81.900 3.15 material for in- 5 ventive example 4 + 5 compound 3: 4-propoxy-2,2,6,6-tetramethyl-piperidin-1-oxyl compound 4: decanedioic acid bis(2,2,6,6-tetramethyl-piperidin-1-oxyl-4-yl) ester compound 5: dodecanoic acid 2,6-diethyl-2,3,6-trimethyl-piperidin-1-oxyl-4-yl ester *bimodal distribution; peak molecular weight (Mp) from high MW peak

TABLE 3 Polymeranalogous reactions Poly- dis- Molecular persity Polymer Mon- Reaction weight (Mn, (Mw/Mn, Example type omer conditions GPC) GPC) Comparison SBS styrene 1 h, 130° C.  102700* 3 B1 Inventive SBS styrene 1 h, 130° C.  104800* example 1 B2 Inventive SBS dode- 1 h, 130° C.  117900* example 2 cyla- crylate Comparison EPDM styrene 1 h, 130° C.  96800 2.86 4 B3 Inventive EPDM styrene 1 h, 130° C. 109600 3.51 example 3 B4 Inventive EPDM styrene 1 h, 130° C.  94700 3.54 example 4 B5 Inventive EPDM styrene 4 h, 130° C. 198400 1.53 example 5 *bimodal distribution; peak molecular weight (Mp) from high MW peak 

What is claimed is:
 1. A process for the preparation of a grafted polymer wherein in a first step A) a stable nitroxyl radical is grafted onto a polymer, which step comprises heating a polymer and a stable nitroxyl radical (NO.) to a temperature between 150° C. to 300° C. in a reactor suitable for mixing a polymer melt; and in a second step B) the grafted polymer of step A) is heated in the presence of an ethylenically unsaturated monomer or oligomer to a temperature at which cleavage of the nitroxyl-polymer bond occurs and polymerization of the ethylenically unsaturated monomer or oligomer is initiated at the polymer radical; maintaining said temperature for further polymerization and afterwards cooling down the mixture to a temperature below 60° C.
 2. A process according to claim 1, wherein a free radical source is additionally present.
 3. A process according to claim 2, wherein the free radical source is a bis-azo compound, a peroxide or a hydroperoxide.
 4. A process according to claim 3 wherein the free radical source is 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-methyl-butyronitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1′-azobis(1-cyclohexanecarbonitrile), 2,2′-azobis(isobutyramide)dihydrate, 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile, dimethyl2,2′-azobisisobutyrate, 2-(carbamoylazo)isobutyronitrile, 2,2′-azobis(2,4,4-trimethylpentane), 2,2′-azobis(2-methylpropane), 2,2′-azobis(N,N′-dimethyleneisobutyramidine), free base or hydrochloride, 2,2′-azobis(2-amidinopropane), free base or hydrochloride, 2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide} or 2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide; acetyl cyclohexane sulphonyl peroxide, diisopropyl peroxy dicarbonate, t-amyl perneodecanoate, t-butyl perneodecanoate, t-butyl perpivalate, t-amylperpivalate, bis(2,4-dichlorobenzoyl)peroxide, diisononanoyl peroxide, didecanoyl peroxide, dioctanoyl peroxide, dilauroyl peroxide, bis(2-methylbenzoyl)peroxide, disuccinic acid peroxide, diacetyl peroxide, dibenzoyl peroxide, t-butyl per 2-ethylhexanoate, bis-(4-chlorobenzoyl)-peroxide, t-butyl perisobutyrate, t-butyl permaleinate, 1,1-bis(t-butylperoxy)3,5,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, t-butyl peroxy isopropyl carbonate, t-butyl perisononaoate, 2,5-dimethylhexane 2,5-dibenzoate, t-butyl peracetate, t-amyl perbenzoate, t-butyl perbenzoate, 2,2-bis(t-butylperoxy)butane, 2,2bis(t-butylperoxy)propane, dicumyl peroxide, 2,5-dimethylhexane-2,5-di-t-butylperoxide, 3-t-butylperoxy 3-phenylphthalide, di-t-amyl peroxide, α,α′-bis(t-butylperoxy isopropyl)benzene, 3,5-bis(t-butylperoxy)3,5-dimethyl 1,2-dioxolane, di-t-butyl peroxide, 2,5-dimethylhexyne-2,5-di-t-butylperoxide, 3,3,6,6,9,9-hexamethyl 1,2,4,5-tetraoxa cyclononane, p-menthane hydroperoxide, pinane hydroperoxide, diisopropylbenzene mono-α-hydroperoxide, cumene hydroperoxide or t-butyl hydroperoxide.
 5. A process according to claim 1 wherein the polymer is polyethylene, polypropylene, polystyrene, a styrene block-copolymer, polybutadiene, polyisoprene, EPDM (ethylene-propylene diene monomer) or EPR (ethylene-propylene rubber).
 6. A process according to claim 1 wherein the stable nitroxyl radical contains a structural element of formula (XXX)

G₁, G₂, G₃, G₄ are independently C₁-C₆alkyl or G₁ and G₂ or G₃ and G₄, or G₁ and G₂ and G₃ and G₄ together form a C₅-C₁₂cycloalkyl group; G₅, G₆ independently are H, C₁-C₁₈alkyl, phenyl, naphthyl or a group COOC₁-C₁₈alkyl.
 7. A process according to claim 6, wherein the compound containing the structural element of formula (XXX) is any of formulae A to S

wherein G₁, G₂, G₃ and G₄ are independently alkyl of 1 to 4 carbon atoms, or G₁ and G₂ together and G₃ and G₄ together, or G₁ and G₂ together or G₃ and G₄ together are pentamethylene; G₅ and G₆ are independently hydrogen or C₁-C₄ alkyl; R, if m is 1, is hydrogen, C₁-C₁₈alkyl which is uninterrupted or interrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic carboxylic acid having 2 to 18 carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or an α,β-unsaturated carboxylic acid having 3 to 5 carbon atoms or of an aromatic carboxylic acid having 7 to 15 carbon atoms, where each carboxylic acid can be substituted in the aliphatic, cycloaliphatic or aromatic moiety by 1 to 3 —COOZ₁₂ groups, in which Z₁₂ is H, C₁-C₂₀alkyl, C₃-C₁₂alkenyl, C₅-C₇cycloalkyl, phenyl or benzyl; or R is a monovalent radical of a carbamic acid or phosphorus-containing acid or a monovalent silyl radical; R, if m is 2, is C₂-C₁₂alkylene, C₄-C₁₂alkenylene, xylylene, a divalent radical of an aliphatic dicarboxylic acid having 2 to 36 carbon atoms, or a cycloaliphatic or aromatic dicarboxylic acid having 8-14 carbon atoms or of an aliphatic, cycloaliphatic or aromatic dicarbamic acid having 8-14 carbon atoms, where each dicarboxylic acid may be substituted in the aliphatic, cycloaliphatic or aromatic moiety by one or two —COOZ₁₂ groups; or R is a divalent radical of a phosphorus-containing acid or a divalent silyl radical; R, if m is 3, is a trivalent radical of an aliphatic, cycloaliphatic or aromatic tricarboxylic acid, which may be substituted in the aliphatic, cycloaliphatic or aromatic moiety by —COOZ₁₂, of an aromatic tricarbamic acid or of a phosphorus-containing acid, or is a trivalent silyl radical, R, if m is 4, is a tetravalent radical of an aliphatic, cycloaliphatic or aromatic tetracarboxylic acid; p is 1, 2 or 3, R₁ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl; when p is 1, R₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl, C₂-C₈alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, or is glycidyl, a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z— or —CONH—Z wherein Z is hydrogen, methyl or phenyl; or when p is 2, R₂ is C₂-C₁₂alkylene, C₆-C₁₂-arylene, xylylene, a —CH₂CH(OH)CH₂—O—B—O—CH₂CH(OH)CH₂— group, wherein B is C₂-C₁₀alkylene, C₆-C₁₅arylene or C₆-C₁₂cycloalkylene; or, provided that R₁ is not alkanoyl, alkenoyl or benzoyl, R₂ can also be a divalent acyl radical of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid or dicarbamic acid, or can be the group —CO—; or R₁ and R₂ together when p is 1 can be the cyclic acyl radical of an aliphatic or aromatic 1,2- or 1,3-dicarboxylic acid; or R₂ is a group

where T₇ and T₈ are independently hydrogen, alkyl of 1 to 18 carbon atoms, or T₇ and T₈ together are alkylene of 4 to 6 carbon atoms or 3-oxapentamethylene; when p is 3, R₂ is 2,4,6-triazinyl; when n is1, R₃ is C₂-C₈alkylene or hydroxyalkylene or C₄-C₂₂acyloxyalkylene; or when n is 2, R₃ is (—CH₂)₂C(CH₂—)₂; when n is 1, R₄ is hydrogen, C₁-C₁₂alkyl, C₃-C₅alkenyl, C₇-C₉aralkyl, C₅-C₇cycloalkyl, C₂-C₄hydroxyalkyl, C₂-C₆-alkoxyalkyl, C₆-C₁₀-aryl, glycidyl, a group of formula —(CH₂)_(m)—COO—Q or of the formula —(CH₂)_(m)—O—CO—Q wherein m is 1 or 2 and Q is C₁-C₄-alkyl or phenyl; or when n is 2, R₄ is C₂-C₁₂alkylene, C₆-C₁₂-arylene, a group —CH₂CH(OH)CH₂—O—D—O—CH₂CH(OH)CH₂— wherein D is C₂-C₁₀alkylene, C₆-C₁₅arylene or C₆-C₁₂cycloalkylene, or a group —CH₂CH(OZ₁)CH₂—(OCH₂CH(OZ₁)CH₂)₂— wherein Z₁ is hydrogen, C₁-C₁₈alkyl, allyl, benzyl, C₂-C₁₂alkanoyl or benzoyl; R₅ is hydrogen, C₁-C₁₂alkyl, allyl, benzyl, glycidyl or C₂-C₆alkoxyalkyl; Q₁ is —N(R₇)— or —O—; E is C₁-C₃alkylene, the group —CH₂CH(R₈)—O— wherein R₈ is hydrogen, methyl or phenyl, the group —(CH₂)₃—NH— or a direct bond; R₇ is C₁-C₁₈alkyl, C₅-C₇-ycloalkyl, C₇-C₁₂aralkyl, cyanoethyl, C₆-C₁₀aryl, the group —CH₂CH(R₈)—OH; or a group of the formula

or a group of the formula

wherein G is C₂-C₆alkylene or C₆-C₁₂arylene and R is as defined above; or R₇ is a group —E—CO—NH—CH₂—OR₆; R₆ is hydrogen or C₁-C₁₈alkyl; Formula (F) denotes a recurring structural unit of a oligomer where T is ethylene or 1,2-propylene, or is a repeating structural unit derived from an α-olefin copolymer with an alkyl acrylate or methacrylate; k is 2 to 100; and R₁₀ is hydrogen, C₁C₁₂alkyl or C₁-C₁₂alkoxy; T₂ has the same meaning as R₄; T₃ and T₄ are independently alkylene of 2 to 12 carbon atoms, or T₄ is a group

T₅ is C₂-C₂₂alkylene, C₅-C₇cycloalkylene, C₁-C₄alkylenedi(C₅-C₇cycloalkylene), phenylene or phenylenedi(C₁-C₄alkylene);

where a, b and c are independently 2 or 3, and d is 0 or 1; e is 3 or 4; E₁ and E₂, being different, are each oxo or imino; E₃ is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl, said phenyl or said naphthyl substituted by chlorine or by alkyl of 1 to 4 carbon atoms, or phenylalkyl of 7 to 12 carbon atoms, or said phenylalkyl substituted by alkyl of 1 to 4 carbon atoms; E₄ is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl or phenylalkyl of 7 to 12 carbon atoms; or E₃ and E₄ together are polymethylene of 4 to 17 carbon atoms, or said polymethylene substituted by up to four alkyl groups of 1 to 4 carbon atoms; and E₆ is an aliphatic or aromatic or aromatic tetravalent radical.
 8. A process according to claim 7, wherein G₁, G₂, G₃ and G₄ are methyl and G₅ and G₆ are hydrogen.
 9. A process according to claim 7 wherein the compound is of the structural formula A, B, O or P, wherein m is 1; R is hydrogen, C₁-C₁₈alkyl which is uninterrupted or interrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic carboxylic acid having 2 to 18 carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or an α,β-unsaturated carboxylic acid having 3 to 5 carbon atoms or of an aromatic carboxylic acid having 7 to 15 carbon atoms; p is 1; R is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₁₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl; R₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl, C₂-C₈alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, or is glycidyl, a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z or —CONH—Z wherein Z is hydrogen, methyl or phenyl.
 10. A process according to claim 9, wherein R is hydrogen, C₁-C₁₈alkyl, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic, carboxylic acid; R₁ is C₁-C₁₂alkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl; R₂ is C₁-C₁₈alkyl, glycidyl, a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z, wherein Z is hydrogen, methyl or phenyl.
 11. A process according to claim 1, wherein the polymer to be grafted on contains unsaturated moieties selected from the group consisting of polydienes, co-, block-, random- and tapered polymers of styrene, terpolymers with diolefins and copolymers with diolefins.
 12. A process according to claim 1, wherein the ethylenically unsaturated monomer or oligomer is selected from the group consisting of styrene, substituted styrene, conjugated dienes, maleic acid anhydride, acrolein, vinyl acetate, (alkyl)acrylic acidanhydrides, (alkyl)acrylic acid salts, (alkyl)acrylic esters or (alkyl)acrylamides.
 13. A process according to claim 1 wherein the ethylenically unsaturated monomer is styrene, α-methyl styrene, p-methyl styrene or a compound of formula CH₂═C(R_(a))—(C═Z)—R_(b), wherein R_(a) is hydrogen or C₁-C₄alkyl, R_(b) is NH₂, OCH₃, glycidyl, unsubstituted C₁-C₁₈alkoxy or hydroxy-substituted C₁-C₁₈alkoxy, unsubstituted C₁-C₁₈alkylamino, di(C₁-C₁₈alkyl)amino, hydroxy-substituted C₁-C₁₈alkylamino or hydroxy-substituted di(C₁-C₁₈alkyl)amino; and Z is oxygen or sulfur.
 14. A process according to claim 13, wherein R_(a) is hydrogen or methyl, R_(b) is NH₂, gycidyl, unsubstituted or with hydroxy substituted C₁-C₄alkoxy, unsubstituted C₁-C₄alkylamino, di(C₁-C₄alkyl)amino, hydroxy-substituted C₁-C₄alkylamino or hydroxy-substituted di(C₁-C₄alkyl)amino; and Z is oxygen.
 15. A process according to claim 14, wherein the ethylenically unsaturated monomer is methylacrylate, ethylacrylate, butylacrylate, isobutylacrylate, tert. butylacrylate, hydroxyethyl-acrylate, hydroxypropylacrylate, dimethylaminoethylacrylate, glycidylacrylates, methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, dimethylaminoethyl(meth)acrylate, glycidyl(meth)acrylates, acrylonitrile, acrylamide or methacrylamide.
 16. A process according to claim 1, wherein the temperature in the second step B) is from 70° C. to 280° C.
 17. A process according to claim 1, wherein the stable nitroxyl radical is present in an amount of from 0.1% to 30% based on the weight of the polymer.
 18. A process according to claim 1, wherein the ratio of the reaction product of step A) to the ethylenically unsaturated monomer or oligomer added in step B) is from 1:1000 to 10:1.
 19. A polymeric radical initiator obtained according to step A) of claim
 1. 20. A polymer obtained according to step A) and B) of the process of claim
 1. 21. A composition comprising a) a polymeric radical initiator prepared according to step A) of claim 1 and b) an ethylenically unsaturated monomer or oligomer.
 22. An adhesive or a compatibilizer for polymer blends or a polymer toughening agent prepared according to claim
 1. 23. A polymeric radical initiator obtainable according to step A) of claim
 2. 24. A polymer obtainable according to step A) and B) of the process of claim
 2. 25. A composition comprising a) a polymeric radical initiator prepared according to step A) of claim 2 and b) an ethylenically unsaturated monomer or oligomer.
 26. An adhesive or a compatibilizer for polymer blends or a polymer toughening agent prepared according to claim
 2. 27. A process according to claim 1, wherein the first step A) is performed in an extruder. 